Coil-type meter

ABSTRACT

Provided is a coil instrument which can maintain a compact configuration even when a rotary shaft at a pointer side is subjected to a deceleration rotation by way of gears. The coil instrument includes a rotor shaft having a rotor magnet and a first gear, a pointer shaft having a second gear connected with the first gear, a housing which pivotally supports the pointer shaft and the rotor shaft in parallel, and a pair of coils which are arranged such that coils opposedly face an outer peripheral surface of the rotor magnet where the second gear is not arranged and give a rotational force to the rotor magnet upon energization thereof.

FIELD OF THE INVENTION

The present invention relates to a coil instrument which rotates a rotormagnet by energizing a coil, for example, a coil instrument incorporatedin a combination meter for a vehicle.

BACKGROUND OF THE INVENTION

As a coil instrument applicable to a meter for vehicle, for example, across-coil instrument has been generally well known. The cross-coilinstrument is called “an air core type movement” and is constituted suchthat a rotor magnet is accommodated in a space defined in a housing, arotor shaft fixed to the rotor magnet is pivotally supported on thehousing, one end of the rotor shaft is protruded to the outside of thehousing, a pointer is mounted on a protruded end of the rotor shaft, anda pair of coils are wound around an outer periphery of the housing insuch a manner that the coils cross at a right angle. The rotor magnet(pointer) is rotated due to a resultant magnetic field generated byenergizing respective coils. By controlling energizing quantities(inputting signals) to respective coils in response to a measuredquantity, the pointer can be angularly moved in response to the measuredquantity.

By the way, in such a cross-coil instrument, it has been known that dueto the winding diameter dimension difference and the magnetic hysteresisor the like of respective coils which are generated by winding a pair ofcoils in layers in a crossing manner, an error occurs on a rotatingangle (an output angle) of the pointer in response to an input signaland this error appears as the indication error. To cope with this, asdisclosed in Japanese Laid-open Patent Publication 27146/1994, it may bepossible to propose an idea that a pointer shaft on which a pointer isfixedly mounted is provided independently from a rotor shaft on which arotor magnet is fixedly mounted and both of these shafts are connectedby way of gears so as to rotate the pointer shaft at a reduced speedcompared with the rotor shaft whereby the occurrence of the indicationerror can be suppressed.

However, the cross-coil instrument disclosed in the above-mentionedpublication has a drawback that in addition to the constitution that apair of coils are wound around the housing in a laminated manner, gearsare further stacked on the housing around which the coils are wound, theheight dimension of the instrument becomes large so that the instrumenthas to become large-sized.

The present invention has been made in view of the above and it is amain object of the present invention to provide a coil instrument whichcan maintain a compact constitution even when a pointer-side rotaryshaft is rotated at a reduced speed by way of gears.

DISCLOSURE OF THE INVENTION

The coil instrument according to the present invention comprises a rotorshaft having a rotor magnet and a first gear rotatable along with therotor magnet, a pointer shaft having a second gear connected with thefirst gear, and a pair of coils arranged such that the coils opposedlyface an outer peripheral surface of the rotor magnet where the secondgear is not arranged and give a rotational force to the rotor magnetupon energization thereof. Due to such a constitution, even when therotary shaft at the pointer side is subjected to the decelerationrotation by way of gears, the compact coil instrument can be provided.

Further, the coil instrument according to the present inventioncomprises a rotor shaft having a rotor magnet and a first gear rotatablealong with the rotor magnet, a pointer shaft having a second gearconnected with the first gear, a housing supporting the pointer shaftand the rotor shaft in parallel, and a pair of coils arranged such thatthe coils opposedly face an outer peripheral surface of the rotor magnetwhere the second gear is not arranged and give a rotational force to therotor magnet upon energization thereof. Due to such a constitution, evenwhen the rotary shaft at the pointer side is subjected to thedeceleration rotation by way of gears, the compact coil instrument canbe provided.

Further, the coil instrument according the present invention comprises arotor shaft having a rotor magnet and a first gear rotatable along withthe rotor magnet, a pointer shaft having a second gear connected withthe first gear, and a pair of coils arranged such that the coilsopposedly face an outer peripheral surface of the rotor magnet where thesecond gear is not arranged in a state that respective winding centralaxes of the coils cross each other with a given crossing angle at or inthe vicinity of the rotary center of the rotor magnet and give arotational force to the rotor magnet upon energization thereof. Due tosuch a constitution, even when the rotary shaft at the pointer side issubjected to the deceleration rotation by way of gears, the compact coilinstrument can be provided.

Further, the coil instrument according to the present inventioncomprises a rotor shaft having a rotor magnet and a first gear rotatablealong with the rotor magnet, a pointer shaft having a second gearconnected with the first gear, a housing supporting the pointer shaftand the rotor shaft in parallel, and a pair of coils arranged such thatthe coils opposedly face an outer peripheral surface of the rotor magnetwhere the second gear is not arranged in a state that respective windingcentral axes of the coils cross each other with a given crossing angleat or in the vicinity of the rotary center of said rotor magnet and givea rotational force to the rotor magnet upon energization thereof. Due tosuch a constitution, even when the rotary shaft at the pointer side issubjected to the deceleration rotation by way of gears, the compact coilinstrument can be provided.

Further, in the coil instrument according to the present invention, thecrossing angle made by the winding center axes of respective coils isset to approximately 90 degrees. Due to such a constitution, themagnetic field vectors generated at respective coils cross at anapproximately right angle and hence, magnetic forces of the coils can bemade to effectively act on the rotor magnet.

Further, in the coil instrument according to the present invention, thecrossing angle made by the winding center axes is set to less than 90degrees. Due to such a constitution, the width dimension of the housingincluding the coils can be made small.

Further, in the coil instrument of the present invention, the rotarycenter of the rotor magnet is positioned closer to the coil side thanthe crossing point made by the winding central axes of the respectivecoils. Due to such a constitution, the width dimension of the housingincluding the coils can be made small.

Further, in the coil instrument of the present invention, the first gearis provided with first continuous teeth on an outer periphery thereof,the second gear includes a accommodating portion which accommodates thefirst gear on an outer periphery thereof, and second continuous teethwhich are meshed with the first continuous teeth are formed on an innerperiphery of the accommodating portion. Due to such a constitution,while realizing the deceleration rotation of the pointer shaft to therotor shaft, the rotor shaft and the pointer shaft can be made toapproach each other and hence, the width dimension of the coilinstrument can be made small by an approaching quantity.

Further, in the coil instrument of the present invention, an outerdiameter of the first gear is smaller than an outer diameter of therotor magnet, an outer diameter of the second gear is larger than theouter diameter of the first gear, and the second gear is arranged suchthat the second gear overlaps the rotor magnet with a given distancetherebetween. Due to such a constitution, it is unnecessary to interposeother gears between these respective gears and hence, the widthdimension of the instrument can be made small.

Further, in the coil instrument of the present invention, a coilsupporting portion which supports the respective coils is contiguouslyformed on the housing. Due to such a constitution, the directions of thewinding center axes of the coils and the crossing angle made by bothwinding center axes can be surely determined and hence, the coils can beheld in a stable manner in a state that the directions of the windingcenter axes of the coils and the crossing angle made by both windingcenter axes are surely determined.

Further, in the coil instrument of the present invention, the rotormagnet 1 and the first and second gears are accommodated in the housing.Due to such a constitution, the height dimension can be decreased.

Further, in the coil instrument of the present invention, the rotationregulation means which regulates the rotation of the pointer shaft isdisposed between the housing and the second gear. Due to such aconstitution, the pointer can be surely stopped at a given position (astart position).

Further, in the coil instrument of the present invention, a given regionof the outer periphery of the housing excluding a region correspondingto the second gear is covered with a cup-shaped magnetic casing. Due tosuch a constitution, the magnetic case can be miniaturized and the costcan be reduced.

Further, in the coil instrument of the present invention, a fixed magnetwhich restricts the movement of the rotor magnet when the respectivecoils are not energized is provided to the housing. Due to such aconstitution, the pointer can be surely held at a given position (astart position) when respective coils are not energized.

Further, in the coil instrument of the present invention, a biasingmember which rotates the pointer shaft in one direction when therespective coils are not energized is provided to the pointer shaft. Dueto such a constitution, the pointer can be surely returned to a givenposition (a start position) when respective coils are not energized andfurther the backlash between the first and second gears can beeliminated.

Further, the coil instrument according to the present inventioncomprises a rotor shaft having a rotor magnet and a first gear rotatablealong with the rotor magnet, a pointer shaft disposed parallel with therotor shaft and having a second gear connected with the first gear, anda pair of coils arranged at an outer peripheral portion in the radialdirection of the rotor magnet where the second gear is not arranged andgive a rotational force to the rotor magnet upon energization thereof,wherein the rotor magnet is partially covered with respective coils. Dueto such a constitution, the coil instrument can increase the generatingtorque while maintaining the thin configuration thereof.

Further, the coil instrument according to the present inventioncomprises a rotor shaft having a rotor magnet and a first gear rotatablealong with the rotor magnet, a pointer shaft having a second gearconnected with the first gear, a housing supporting the pointer shaftand the rotor shaft in parallel, and a pair of coils arranged at anouter peripheral surface in the radial direction of the rotor magnetwhere the second gear is not arranged in a state that respective windingcentral axes of the coils cross each other with a given crossing angleat or in the vicinity of the rotary center of the rotor magnet and givea rotational force to the rotor magnet upon energization thereof,wherein the rotor magnet is partially covered with respective coils. Dueto such a constitution, the coil instrument can increase the generatingtorque while maintaining the thin configuration thereof.

Further, in the coil instrument according to the present invention, thewinding diameter of the coils corresponding to at least a radialperipheral surface of the rotor magnet is gradually increased toward therotor shaft. Due to such a constitution, while ensuring an enoughwinding quantity, the coil instrument can make the structure compactwhereby the space efficiency can be enhanced.

Further, in the coil instrument according to the present invention, thewinding frame portions around which the respective coils are wound arecontiguously formed on the housing. Due to such a constitution, thedirections of the winding center axes of respective coils and thecrossing angle made by both winding center axes can be surely determinedand hence, the coils can be held in a stable manner in a state that thedirections of the winding center axes of the coils and the crossingangle made by both winding center axes are surely determined.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 and FIG. 2 are views showing a first embodiment of the presentinvention, wherein FIG. 1 is a plan view of a coil instrument and FIG. 2is a cross-sectional view taken along a line A—A of FIG. 1.

FIG. 3 is a plan view of a coil instrument showing a second embodimentof the present invention.

FIG. 4 is a plan view showing a third embodiment of the presentinvention.

FIG. 5 is a cross-sectional view showing a fourth embodiment of thepresent invention.

FIG. 6 to FIG. 8 are views showing a fifth embodiment of the presentinvention, wherein FIG. 6 is a plan view of a coil instrument, FIG. 7 isa cross-sectional view taken along a line A—A of FIG. 6 and FIG. 8 is across-sectional view taken along a line B—B of FIG. 6.

DETAILED DESCRIPTION OF THE INVENTION

In FIG. 1 and FIG. 2 which show a first embodiment of the presentinvention, a coil instrument includes a rotor shaft 3 provided with arotor magnet 1 and a first gear 2, a pointer shaft 5 provided with asecond gear 4 which is connected by meshing with the first gear 2 andmounting a pointer P thereon, a housing 6 which pivotally supports therotor shaft 3 and the pointer shaft 5 in parallel in a state thatrespective gears 2, 4 are connected and accommodates the rotor magnet 1and the first and second gears 2, 4, a pair of coils 7, 8 which arepositioned on an outer periphery of the housing 6 and are arranged atthe side of the rotor magnet 1 in an opposed manner and give arotational force to the rotor magnet 1 upon energization thereof, and amagnetic case 9 which covers a given region of the housing 6.

The rotor magnet 1 is made of, for example, a disc-like plastic magnetwhich is magnetized with two poles, that is, a N pole and a S pole. Thefirst gear 2 is made of a gear having a desired number of continuousteeth on an outer periphery thereof. In FIG. 2, the first gear 2 isfixedly mounted on the rotor shaft 3 such that the rotor magnet 1 ispositioned below and the first gear 2 is positioned above.

The second gear 4 has a diameter greater than a diameter of the firstgear 2, has a larger number of continuous teeth than the first gear 2and is fixedly mounted on the pointer shaft 5. In FIG. 2, the secondgear 4 is extended toward the first gear 2 side and is meshed with thefirst gear 2 such that the second gear 4 is positioned above the rotormagnet 1 and overlaps the rotor magnet 1 with a suitable spacetherebetween.

The housing 6 is made of synthetic resin and, as shown in FIG. 2, thehousing 6 is divided and formed into a first frame body 61 positionedbelow and a second frame body 62 positioned above. A cavity whichbecomes an accommodating portion S is formed between the first andsecond frame bodies 61, 62 and the rotor shaft 3 and the pointer shaft 5are pivotally supported on the housing 6. The pointer shaft 5 has oneend thereof protruded to the outside from the housing 6.

As shown in FIG. 2, the accommodating portion S is formed by a firsthousing portion 63 which forms a first accommodating portion S1positioned below and accommodating the rotor magnet 1 and a secondhousing portion 64 which forms a second accommodating portion S2positioned above and accommodating the first and second gears 2, 4.Respective accommodating portions S1, S2 formed by these housingportions 63, 64 are communicated with each other corresponding to therelationship between the rotor magnet 1 and the second gear 4 overlappedwith the previously-mentioned space and the relationship between thefirst gear 1 and the second gear 4 connected with each other. Further,as shown in FIG. 1, respective housing portions 63, 64 have arcuateplanar shapes corresponding to the outer-diameter shapes of the rotormagnet 1 and the second gear 4.

As shown in FIG. 1, the coils 7, 8 are arranged such that they opposedlyface an outer peripheral side surface of the rotor magnet 1(radial-directional outer peripheral portion of the rotor magnet 1),wherein at an outer peripheral region of the first housing portion 63which is positioned at a side opposite to the second housing portion 64which becomes the second gear 4 accommodating side, axial linesextending toward the rotor magnet 1 along respective winding center axesC1, C2 cross each other at the center of rotation RC (a crossing pointCP) of the rotor magnet 1 and a crossing angle made by respectivewinding center axes C1, C2 in this state becomes approximately 90degrees. Here, the coils 7, 8 are wound around a pair of coil supportportions 65, 66 respectively extending from the outer peripheral surfaceof the first housing portion 63 (the first frame body 61) toward theoutside in the radial direction of the rotor magnet 1 and are supportedon the housing 6.

In this manner, although the magnetic case 9 having a cup shape ismounted on the housing 6 around which the coils 7, 8 are wound,according to this embodiment, a given region of the housing 6 excludinga region corresponding to the second gear 4, that is, only a bottomportion and its periphery of the first housing portion 63 which do notinclude the region corresponding to the second gear 4 are covered withthe magnetic case 9.

In the coil instrument having such a constitution, by energizingrespective coils 7, 8, magnetic field vectors respectively act along thewinding center axes C1, C2 and the rotor magnet 1 (the rotor shaft 3) isrotated corresponding to the intensities of respective magnetic fieldvectors. This rotation is transmitted to the pointer shaft 5 by way ofthe first gear 2 and the second gear 4 and the pointer P fixedly mountedon the pointer shaft 5 performs the angular movement.

Here, the first gear 2 and the second gear 4 have set their respectivegear ratio to 1:3, for example, such that the second gear 4 is rotatedat a low speed (a reduced speed) compared to the first gear 2. Due tosuch a reduced-speed or a deceleration operation, the angular movementof the pointer P with the least indication error to the input signal canbe obtained so that the linearity (linear characteristics) of theindication characteristics can be ensured whereby the highly accurateindication can be performed. Provided that the deceleration operation isperformed at the pointer shaft 5 side, the gear ratio between the firstand second gears 2, 4 can be set to any arbitrary value.

Further, a fixed-side contact portion 62 a which has a portion thereofextended toward the second gear 4 in the second accommodating portion S2and is formed on the housing 6 (here, the second frame body 62) and amovable-side contact portion 4 a which has a portion thereof extendedtoward an inner wall surface of the second frame body 62 in the secondaccommodating portion S2 is formed on the second gear 4. Themovable-side contact portion 4 a and the fixed-side contact portion 62 aconstitute rotation regulating means which regulates the rotation of thepointer shaft 5. The position at which both contact portions 4 a, 62 acome into contact with each other is set as a start position of thepointer P (for example, a minimum indication position).

In this manner, by performing the regulation of rotation of the pointerP between the second gear 4 fixedly mounted on the pointer shaft 5 onwhich the pointer P is mounted and the housing 6, the irregularities ofthe stop position of the pointer P can be decreased compared with a casein which the regulation of the rotation is performed at the rotor shaft3 side.

Here, the regulation of rotation of the pointer P may be performed toregulate not only the start position of the pointer P but also themaximum indication position. When the maximum indication position isregulated along with the start position regulation in this manner, forexample, a movable-side contact portion (not shown in the drawing)separate from the movable-side contact portion 4 a may be formed on thesecond gear 4.

Further, as shown in FIG. 1, a fixed magnet 10 is arranged on thehousing 6 (here, the first frame body 61) at a position where the fixedmagnet 10 faces the outer peripheral surface of the rotor magnet 1 in anopposed manner with a suitable space therebetween. Due to this fixedmagnet 10, the movement of the rotor magnet 1 can be restricted whenrespective coils 7, 8 are not energized so that the pointer P can bemaintained at the start position which becomes the position where themovable-side contact portion 4 a and the fixed-side contact portion 62 acome into contact with each other. Here, it is desirable that the fixedmagnet 10 is mounted such that the rotor magnet 1 can bias themovable-side contact portion 4 a toward the fixed-side contact portion62 a side.

The provision of such a fixed magnet 10 makes a magnetic force of thefixed magnet 10 always act on the rotor magnet 1 and hence becomes afactor which generates an indication error. However, as mentioned above,according to this embodiment, since the coil instrument is constitutedsuch that the pointer shaft 5 is operated at a reduced speed (rotation)compared with the rotor shaft 3, it gives rise to an advantageous effectthat even when the magnetic influence derived from the fixed magnet 10is present, this magnetic influence hardly appears as the indicationerror.

Further, in the housing 6 (here, the second frame body 62), a biasingmember 11 made of a hair spring which rotates the rotor magnet 1 in onedirection (reduced speed indication direction side) when respectivecoils 7, 8 are not energized is mounted on a portion of the pointershaft 5 protruded from the housing 6. Due to this biasing member 11, thepointer P can be returned to the start position even when respectivecoils 7, 8 are not energized and, at the same time, a backlash presentbetween the first and second gears 2, 4 can be eliminated.

As has been described heretofore, according to this embodiment, the coilinstrument includes the rotor shaft 3 provided with the rotor magnet 1and the first gear 2 rotated together with the rotor magnet 1, thepointer shaft 5 provided with the second gear 4 connected with the firstgear 2, the housing 6 which pivotally supports the rotor shaft 3 and thepointer shaft 5 in parallel and a pair of coils 7, 8 which give therotational force to the rotor magnet 1. Further, respective coils 7, 8are arranged such that they opposedly face the outer peripheral surfaceof the rotor magnet 1 where the second gear 4 is not arranged.Particularly, respective coils 7, 8 are arranged such that theyopposedly face the outer peripheral surface of the rotor magnet 1 wheretheir winding center axes C1, C2 cross at the center of rotation of therotor magnet 1 while making the given crossing angle between them. Dueto such a constitution, the coils 7, 8 are not stacked on the housing 6so that even when the pointer shaft 5 is rotated at a reduced speed byway of gears, the height dimension of the instrument can be decreasedwhereby the coil instrument can be miniaturized. Further, setting thearrangement position of the coils 7, 8 at the outer peripheral surfaceof the rotor magnet 1 on which the second gear 4 is not arranged, thecoils 7, 8 and the second gear 4 are not overlapped in the axialdirection of the rotor shaft 3 and the pointer shaft 5 whereby the coilinstrument can be made thin correspondingly.

Further, according to this embodiment, since the crossing angle made bythe winding center axes C1, C2 of respective coils 7, 8 is set toapproximately 90 degrees, the magnetic field vectors generated in thecoils 7, 8 cross each other at an approximately right angle so that themagnetic forces generated by the coils 7, 8 can be made to act on therotor magnet 1 more effectively.

Further, according to this embodiment, the outer diameter of the firstgear 2 is set smaller than the outer diameter of the rotor magnet 1 andthe outer diameter of the second gear 4 is set larger than the outerdiameter of the first gear 2, and the second gear 4 is arranged suchthat the second gear 4 overlaps the rotor magnet 1 with a given distancetherebetween so that it is unnecessary to provide other gears betweenrespective gears 2, 4 whereby the width dimension of the instrument canbe made small.

Further, according to this embodiment, by continuously forming the coilsupport portions 65, 66 which support respective coils 7, 8 on thehousing 6, the directions of the winding center axes C1, C2 of the coils7, 8 and the crossing angle made by these axes can be surely determined.Further, in the state that the directions of the winding center axes C1,C2 and the crossing angle are surely determined in such a manner, thecoils 7, 8 can be held in a stable manner.

Further, according to this embodiment, since the rotor magnet 1 and thefirst and second gears 2, 4 are accommodated in the housing 6, theheight dimension can be reduced.

Further, according to this embodiment, since the rotation regulatingmeans consisting of the movable-side contact portion 4 a and thefixed-side contact portion 62 a which regulates the rotation of thepointer shaft 5 is disposed between the housing 6 and the second gear 4,the pointer P can be surely stopped at the given position (the startposition).

Further, according to this embodiment, since the fixed magnet 10 whichrestricts the movement of the rotor magnet 1 when respective coils 7, 8are not energized is mounted on the housing 6, the pointer P can besurely held at the given position (the start position) when respectivecoils 7, 8 are not energized.

Further, according to this embodiment, since the biasing member 11 madeof the hair spring which rotates the rotor magnet 1 in one directionwhen respective coils 7, 8 are not energized is mounted on the pointershaft 5, even when respective coils 7, 8 are not energized, it becomespossible to return the pointer P to the given position (start position).Further, the backlash between the first and second gears 2, 4 can beeliminated.

Further, according to this embodiment, since the given outer peripheralregion of the housing 6 excluding the region corresponding to the secondgear 4 is covered with the cupshaped magnetic case 9, the magnetic case9 can be miniaturized and the manufacturing cost thereof can be reduced.

In this embodiment, the case in which the rotary center RC of the rotormagnet 1 and the crossing point CP of the winding center axes C1, C2 ofrespective coils 7, 8 agree with each other is exemplified. However, asthe second embodiment of the present invention, as shown in FIG. 3, itmay be possible to set the crossing point CP of the winding center axesC1, C2 of respective coils 7, 8 in the vicinity of the rotary center RCof the rotor magnet 1. Here, “in the vicinity of the rotary center RC”includes a center region of the rotor magnet 1 which can drive the rotormagnet 1 as an instrument at the time of setting the crossing point CPof respective coils 7, 8 in the inside of the rotor magnet 1.

Further, particularly, by setting the crossing point CP of the windingcenter axes C1, C2 of respective winding coils 7, 8 closer to thepointer shaft 5 side than the rotary center RC of the rotor magnet 1 (bysetting the rotary center RC of the rotor magnet 1 closer to the coil 7,8 side than the crossing point CP of the winding center axes C1, C2 ofrespective coils 7, 8), the width dimension W1 (see FIG. 3) of thehousing 6 including the coils 7, 8 can be made small.

Although the crossing angle made by the winding center axes C1, C2 ofrespective coils 7, 8 is set to approximately 90 degrees in thepreviously-mentioned first and second embodiments, as shown in FIG. 4,as a third embodiment of the present invention, it may be possible toset the crossing angle made by the winding center axes C1, C2 to a valuesmaller than 90 degrees (80 degrees in the drawing). By setting thecrossing angle to a value smaller than 90 degrees in this manner, thewidth dimension W2 (see FIG. 4) of the housing 6 including the coils 7,8 can be made small.

The first to third embodiments have explained the case in which thefirst and second gears 2, 4 have their outer peripheries meshed witheach other. However, as shown in FIG. 5, as a fourth embodiment of thepresent invention, first continuous teeth 2 a may be formed on an outerperiphery of the first gear 2, a gear accommodating portion 4 b whichaccommodates the first gear 2 may be formed on the outer periphery ofthe second gear 4 and second continuous teeth 4 c which are meshed withthe first continuous teeth 2 a may be formed on an inner periphery ofthis gear accommodating portion 4 b. Due to such a constitution, whileensuring the deceleration rotation of the pointer shaft 5 compared tothe rotor shaft 3, the rotor shaft 3 and the pointer shaft 5 can be madeto approach each other so that the width dimension of the coilinstrument can be reduced by an approaching quantity compared to thecoil instruments of the first to fourth embodiments.

Further, the coil instrument according to a fourth embodiment of thepresent invention is provided with a notched portion 64 a for partiallyexposing an end portion of the second gear 4 from the second housingportion 64 so that the width dimension of the coil instrument can befurther decreased due to this notched portion 64 a.

Further, in the coil instrument according to the fourth embodiment ofthis invention, the rotor shaft 3 is integrally formed with the firstframe body 61 thus constituting a fixed shaft supported on the housing6. A rotor magnet 1 and a first gear 2 which moves corresponding to therotor magnet 1 are rotatably supported on this rotor shaft 3 which isconstituted by a fixed shaft. In this case, the first gear 2 isintegrally and contiguously formed with the rotor magnet 1 made of aplastic magnet, for example. In this manner, since the rotor shaft 3 isconstituted by the fixed shaft which is integrally formed with thehousing 6, the number of parts can be reduced.

Subsequently, a fifth embodiment of the present invention is explained.

As shown in FIG. 6 to FIG. 8, a coil instrument includes a rotor shaft 3provided with a rotor magnet 1 and a first gear 2, a pointer shaft 5provided with second gear 4 which is connected by meshing with the firstgear 2 and mounting a pointer P on a distal end thereof and rotating thepointer P corresponding to the rotation of the second gear 4, a housing6 which pivotally supports the rotor shaft 3 and the pointer shaft 5 inparallel in a state that respective gears 2, 4 are connected andaccommodates the rotor magnet 1 and the first and the second gears 2, 4,a pair of coils 7, 8 which are arranged on an outer periphery in theradial direction of the rotor magnet 1 and give a rotational force tothe rotor magnet 1 upon energization thereof, and a magnetic case 9 madeof metal which covers a given region of the housing 6.

The rotor magnet 1 is made of, for example, a disc-like plastic magnetwhich is magnetized with four poles such that an N pole and an S poleare alternately arranged. The first gear 2 is made of a gear having adesired number of continuous teeth on an outer periphery thereof. InFIG. 2, the rotor magnet 1 and the first gear 2 are fixedly mounted onthe rotor shaft 3 such that the rotor magnet 1 is positioned below andthe first gear 2 is positioned above.

The second gear 4 has a diameter greater than a diameter of the firstgear 2, has a larger number of continuous teeth on an outer perpherythereof than the first gear 2 and is fixedly mounted on the pointershaft 5. In FIG. 7, the second gear 4 is extended toward the first gear2 side and is meshed with the first gear 2 such that the second gear 4is positioned above the rotor magnet 1 and overlaps the rotor magnet 1with a suitable space.

The housing 6 is made of synthetic resin and, as shown in FIG. 7, thehousing 6 is divided and formed into a first frame body 61 positionedbelow and a second frame body 62 positioned above. A cavity whichbecomes an accommodating portion S is formed between the first and thesecond frame bodies 61, 62 and the rotor shaft 3 and the pointer shaft 5are pivotally supported on the housing 6.

As shown in FIG. 7, the accommodating portion S is formed by a firstaccommodating portion S1 which is positioned below and accommodates therotor magnet 1 and a second accommodating portion S2 which is positionedabove and accommodates the first and second gears 2, 4. Respectiveaccommodating portions S1, S2 are communicated with each othercorresponding to the relationship between the rotor magnet 1 and thesecond gear 4 overlapped with a space therebetween and the relationshipbetween the first gear 2 and the second gear 4 connected with eachother.

Further, in this case, in the housing 6 region corresponding to theouter periphery in the radial direction of the rotor magnet 1 at whichthe second gear 4 is not arranged, winding frame portions 630, 640 areformed of first and second frame bodies 61, 62 and the coils 7, 8 arewound around these winding frame portions 630, 640.

As shown in FIG. 6 and FIG. 8, the winding frame portions 630, 640respectively include winding portions 650 around which respective coils7, 8 are wound and a pair of opposing walls 660 which sandwich thiswinding portion 650 such that both end portions of respective coils 7, 8are held by these opposing walls 660. In this embodiment, the windingportion 650 is formed such that the contour thereof which corresponds tothe peripheral surface in the radial direction of the rotor magnet 1 isgradually increased toward the rotor shaft 3.

By winding the coils 7, 8 around the winding frame portions 630, 640,the coils 7, 8 are positioned at the outer periphery (outer peripheralsurface) in the radial direction of the rotor magnet 1 where the secondgear 4 is not arranged, wherein the winding diameters corresponding tothe radial peripheral surface of the rotor magnet 1 are graduallyincreased toward the rotor shaft 3. Here, axial lines extended towardthe rotor shaft 3 side along the winding center axes C1, C2 ofrespective coils 7, 8 cross at the center of rotation RC of the rotormagnet 1 (crossing point CP). The crossing angle made by respectivewinding center axes C1, C2 here is set to approximately 135 degrees inthis embodiment. Further, on the rotor magnet 1 sides of respectivecoils 7, 8, covering portions 71, 81 which partially cover the rotormagnet 1 are formed.

The covering portions 71, 81 partially cover the rotor magnet 1 suchthat the outer peripheral portion in the radial direction of the rotormagnet 1 is accommodated in the inside thereof.

In this manner, although a cup-shaped magnetic case 9 is mounted on thehousing 6 around which coils 7, 8 are wound, in this embodiment, adesired region of the housing 6 excluding a region corresponding to thesecond gear 4, that is, only a bottom portion of the first housingportion 63 and its periphery which do not include the regioncorresponding the second gear 4 is covered with the magnetic case 9.

In the coil instrument having such a constitution, respective magneticfield vectors act along the winding center axes C1, C2 of the coils 7, 8by energizing respective coils 7, 8. Corresponding to the intensities ofthese respective magnetic field vectors, the rotor magnet 1 magnetizedwith four poles (the rotor shaft 3) is rotated and the rotational forceis transmitted to the pointer shaft 5 by way of the first gear 2 and thesecond gear 4 so that the pointer P fixedly mounted on the pointer shaft5 performs the angular movement.

Here, respective gear ratios of the first gear 2 and the second gear 4are determined to 1:5, for example, such that the second gear 4 isrotated at a low speed (deceleration) compared to the first gear 2. Dueto this deceleration operation, the angular movement of the pointer Pexhibiting a small indication error in response to an input signal canbe realized so that the linearity (linear characteristics) of theindication characteristics can be ensured whereby the highly accurateindication can be performed. So long as the deceleration operation canbe performed at the pointer shaft 5 side, the gear ratios of the firstand second gear 2, 4 can be arbitrarily determined.

As has been described above, according to this embodiment, the rotorshaft 3 which holds the rotor magnet 1 and the first gear 2 which isrotated together with this rotor magnet 1 is provided. The pointer shaft5 which holds the second gear 4 being connected with and driven by thefirst gear 2 and drives the pointer P corresponding to the rotation ofthis second gear 4 is provided. The housing 6 which supports thesepointer shaft 5 and the rotor shaft 3 in parallel is provided. A pair ofcoils 7, 8 which are arranged such that respective winding center axesC1, C2 cross each other with the crossing angle of approximately 45degrees at the rotary center CR of the rotor magnet 3 and give therotational force to the rotor magnet 1 by energization are mounted onthe outer periphery in the radial direction of the rotor magnet 1 wherethe second gear 4 is not arranged. Further, respective coils 7, 8 areprovided with the covering portions 71, 81 which partially cover theouter peripheral portion in the radial direction of the rotor magnet 1.Due to such a constitution, while maintaining the thin structure byarranging the coils 7, 8 at the outer peripheral portion in the radialdirection of the rotor magnet 1, the magnetic field acting on the rotormagnet 1 at the covering portions 71, 81 of the coils 7, 8 can beincreased so that the output torque of the rotor can be increased.Further, since the number of coils 7, 8 necessary in operation can beminimized, the coil instrument can be constituted by the number of thecoils 7, 8 smaller than conventional coil instrument so that thedimension of the configuration can be reduced and the manufacturing costcan be also reduced.

Further, in this embodiment, since respective coils 7, 8 are wound suchthat the winding diameter corresponding to the at least radialperipheral surface of the rotor magnet is gradually increased toward therotor shaft 3, while ensuring a sufficient winding quantity, thedimension of the configuration of the coils 7, 8 can be reduced so thatthe space efficiency can be enhanced.

Further, according to this embodiment, the winding frame portions 63, 64are contiguously formed on the housing 6 which supports both of therotor shaft 3 and the pointer shaft 5 and respective coils 7, 8 arewound around these winding frame portions 63, 64 and hence, thedirections of the winding center axes C1, C2 of respective coils 7, 8and the crossing angle made by these winding center axes C1, C2 can besurely determined. Further, the coils can be held in a stable manner inthe state that the directions of these winding center axes and thecrossing angle can be surely determined.

Although the rotor magnet 1 magnetized with four poles constituted byalternating an N pole and an S pole is used and the crossing angle madeby the winding center axes C1, C2 of respective coils 7, 8 is set toapproximately 135 degrees in this embodiment, the number of energizationof the rotor magnet 1 and the crossing angle made by the winding centeraxes C1, C2 can be arbitrarily determined. For example, the number ofmagnetization of the rotor magnet 1 may be set to six poles and thecrossing angle made by the winding center axes C1, C2 of respectivecoils 7, 8 may be set to approximately 150 degrees.

Further, according to this embodiment, the outer diameter of the firstgear 2 is set smaller than the outer diameter of the rotor magnet 1, theouter diameter of the second gear 4 is set larger than the outerdiameter of the first gear 2, and the second gear 4 is arranged suchthat the second gear 4 overlaps the rotor magnet 1 with a given distancetherebetween and hence, it is unnecessary to interpose other gearsbetween respective gears 2, 4 whereby the width dimension of theinstrument can be made small.

Further, according to this embodiment, a case in which the rotary centerRC of the rotor magnet 1 agrees with the crossing pointer CP of thewinding center axes C1, C2 of respective coils 7, 8 is exemplified.However, the crossing point CP of the winding center axes C1, C2 ofrespective coils 7, 8 may be set in the vicinity of the rotary center RCof the rotor magnet 1. Here, “in the vicinity of the rotary center RC”includes a central region of the rotor magnet 1 which can drive therotor magnet 1 as an instrument at the time of setting the crossingpoint CP of respective coils 7, 8 within the rotor magnet 1.

Industrial Applicability

The application of the present invention is not limited to a combinationmeter for a vehicle and the present invention is widely applicable asdrive sources of various meters mounted on ships and airplanes, forexample.

What is claimed is:
 1. A coil instrument comprising a rotor shaft havinga rotor magnet and a first gear rotatable along with said rotor magnet,a pointer shaft disposed parallel with said rotor shaft and having asecond gear connected with said first gear, and a pair of coils disposedin a non-overlapping arrangement relative to one another, said pair ofcoils disposed radially adjacent said rotor magnet and facing a radialperipheral surface of said rotor magnet on a side of said rotor magnetopposite said second gear so as to be non-overlapping with said secondgear and give a rotational force to said rotor magnet upon energizationthereof.
 2. A coil instrument according to claim 1 wherein an outerdiameter of said first gear is smaller than an outer diameter of saidrotor magnet, an outer diameter of said second gear is larger than theouter diameter of said first gear, and said second gear is arranged suchthat said second gear overlaps said rotor magnet with a given distancetherebetween.
 3. A coil instrument according to claim 1 wherein saidrotor magnet and said first and second gears are accommodated in saidhousing.
 4. A coil instrument according to claim 1 wherein a fixedmagnet which restricts the movement of said rotor magnet when saidrespective coils are not energized is provided.
 5. A coil instrumentaccording to claim 1 wherein a biasing member which rotates said pointershaft in one direction when said respective coils are not energized isprovided.
 6. A coil instrument comprising a rotor shaft having a rotormagnet and a first gear rotatable along with said rotor magnet, apointer shaft having a second gear connected with said first gear, ahousing supporting said pointer shaft and said rotor shaft in parallel,and a pair of coils disposed in a non-overlapping arrangement relativeto one another, said pair of coils disposed radially adjacent said rotormagnet and facing a radial peripheral surface of said rotor magnet on aside of said rotor magnet opposite said second gear so as to benon-overlapping with said second gear and so as to give a rotationalforce to said rotor magnet upon energization thereof.
 7. A coilinstrument according to claim 6 wherein a coil supporting portion whichsupports said respective coils is contiguouly formed on said housing. 8.A coil instrument according to claim 6 wherein rotation regulation meanswhich regulates the rotation of said pointer is disposed between saidhousing and said second gear.
 9. A coil instrument according to claim 6wherein a given region of said housing excluding a region correspondingsaid second gear is covered with a cup-shaped magnetic casing.
 10. Acoil instrument comprising a rotor shaft having a rotor magnet and afirst gear rotatable along with said rotor magnet, a pointer shaftdisposed parallel with said rotor shaft and having a second gearconnected with said first gear, and a pair of coils disposed in anon-overlapping arrangement relative to one another, said pair of coilsdisposed radially adjacent said rotor magnet and facing a radialperipheral surface of said rotor magnet on a side of said rotor magnetopposite said second gear so as to be non-overlapping with said secondgear in a state that respective winding central axes of said coils crosseach other with a given crossing angle at or in the vicinity of therotary center of said rotor magnet and so as to give a rotational forceto said rotor magnet upon energization thereof.
 11. A coil instrumentaccording to claim 10 wherein said crossing angle is set atapproximately 90 degrees.
 12. A coil instrument according to claim 10wherein said crossing angle is less than 90 degrees.
 13. A coilinstrument according to claim 10 wherein the rotary center of said rotormagnet is positioned closer to said coil side than the crossing point ofsaid winding central axes of said respective coils.
 14. A coilinstrument comprising a rotor shaft having a rotor magnet and a firstgear rotatable along with said rotor magnet, a pointer shaft having asecond gear connected with said first gear, a housing supporting saidpointer shaft and said rotor shaft in parallel, and a pair of coilsdisposed in a non-overlapping arrangement relative to one another, saidpair of coils disposed radially adjacent said rotor magnet and facing aradial peripheral surface of said rotor magnet on a side of said rotormagnet opposite said second gear so as to be non-overlapping with saidsecond gear in a state that respective winding central axes of saidcoils cross each other with a given crossing angle at or in the vicinityof the rotary center of said rotor magnet and so as to give a rotationalforce to said rotor magnet upon energization thereof.
 15. A coilinstrument comprising a rotor shaft having a rotor magnet and a firstgear rotatable along with said rotor magnet, a pointer shaft disposedparallel with said rotor shaft and having a second gear connected withsaid first gear, and a pair of coils arranged such that said coilsopposedly face an outer peripheral surface of said rotor magnet wheresaid second gear is not arranged and give a rotational force to saidrotor magnet upon energization thereof, wherein said first gear isprovided with first continuous teeth on an outer periphery thereof, saidsecond gear includes an accommodating portion which accommodates saidfirst gear on an outer periphery thereof, and second continuous teethwhich are meshed with said first continuous teeth are formed on an innerperiphery of said accommodating portion.
 16. A coil instrumentcomprising a rotor shaft having a rotor magnet and a first gearrotatable along with said rotor magnet, a pointer shaft disposedparallel with said rotor shaft and having a second gear connected withsaid first gear, and a pair of coils disposed in a non-overlappingarrangement relative to one another, said pair of coils being arrangedat an outer peripheral portion in the radial direction of said rotormagnet distal from said second gear so as to be non-overlapping withsaid second gear and so as to give a rotational force to said rotormagnet upon energization thereof, wherein said rotor magnet is partiallycovered with said respective coils.
 17. A coil instrument according toclaim 16 wherein said coils are wound such that the winding diametercorresponding to at least a radial peripheral surface of said rotormagnet is gradually increased toward said rotor shaft.
 18. A coilinstrument comprising a rotor shaft having a rotor magnet and a firstgear rotatable along with said rotor magnet, a pointer shaft having asecond gear connected with said first gear, a housing supporting saidpointer shaft and said rotor shaft in parallel, and a pair of coilsdisposed in a non-overlapping arrangement relative to one another, saidpair of coils being arranged at an outer peripheral portion in theradial direction of said rotor magnet distal from said second gear so asto be non-overlapping with said second gear in a state that respectivewinding central axes of said coils cross each other with a givencrossing angle at or in the vicinity of the rotary center of said rotormagnet and so as to give a rotational force to said rotor magnet uponenergization thereof, wherein said rotor magnet is partially coveredwith said respective coils.
 19. A coil instrument according to claim 18wherein winding frame portions around which said respective coils arewound are contiguously formed on said housing.